Amorphous esomeprazole hydrate

ABSTRACT

The present invention relates to a novel amorphous form of esomeprazole hydrate, to a process for its preparation and to a pharmaceutical composition containing it. Thus, tetrahydrofuran and water are added to esomeprazole potassium salt at 25-30° C., cooled to 20° C. and then the pH is adjusted to 7.5-8.0 with acetic acid. The reaction mass is cooled to 5° C., stirred for 2 to 3 hours at 0-5° C., filtered the mass, washed with chilled mixture of water and tetrahydrofuran (2:1) and again washed with water. The wet cake is dried at 30-35° C. under vacuum to reach the moisture content to 25-30%. The solid is again dried in rotovapour at 25-30° C. under nitrogen atmosphere to give amorphous esomeprazole hydrate.

This specification is a Divisional of U.S. application Ser. No.11/570,473 filed Dec. 12, 2006, now U.S. Pat. No. 7,563,812 which is aNational Stage Entry of PCT/IN2005/000197, filed Jun. 15, 2005.

FIELD OF THE INVENTION

The present invention relates to a novel amorphous form of esomeprazolehydrate, to a process for its preparation and to a pharmaceuticalcomposition containing it.

BACKGROUND OF THE INVENTION

Omeprazole, chemically5-methoxy-2-[[(4-methoxy-3,5-dimethyl-2-pyridinyl)methyl]sulfinyl]-1H-benzimidazoleand its therapeutic uses are disclosed in European Patent No. 5129.Omeprazole is a well-known gastric acid secretion inhibitor, and isuseful as an anti ulcer agent. Omeprazole has a stereogenic center atsulfur and therefore exist as two optical isomers such as R-omeprazoleand S-omeprazole (esomeprazole).

The salts of the enantiomers of omeprazole are described in WO 94/27988.PCT Publication No. WO 98/28294 disclosed esomeprazole in an amorphousform, a partly crystalline form A, and a substantially crystalline formB.

PCT Publication No. WO 2004/076440 A1 described crystalline forms, FormI and Form II, of esomeprazole, and its hydrates. PCT Publication No. WO2004/020436 A1 described amorphous hydrates of esomeprazole magnesiumand process for their preparation. PCT Publication No. WO 2004/002982 A2described amorphous form esomeprazole free base and process for itspreparation.

U.S. Pat. No. 6,369,085 described crystalline forms of esomeprazolemagnesium, esomeprazole magnesium dihydrate, esomeprazole magnesiumtrihydrate and esomeprazole potassium.

The alkaline salts of (S)-enantiomer of omeprazole (esomeprazole), thepharmaceutical preparations of these salts and the method of treatmentof gastric acid-related diseases using them are disclosed in U.S. Pat.No. 4,738,974, U.S. Pat. No. 5,877,192 and U.S. Pat. No. 5,714,504.

We have discovered a stable novel amorphous form of esomeprazolehydrate. The novel amorphous esomeprazole hydrate is stable over thetime and has good flow properties and so, the novel amorphous hydrate issuitable for formulating esomeprazole.

The object of the present invention is to provide a stable novelamorphous form of esomeprazole hydrate, process for preparing it andpharmaceutical composition containing it.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, there is provided a novelamorphous form of esomeprazole hydrate. The water content of theamorphous form of esomeprazole hydrate is between 3.0 and 5.0% by weightof amorphous form of esomeprazole hydrate, typically between 3.5 and4.5% by weight of amorphous form of esomeprazole hydrate.

The amorphous form of esomeprazole hydrate, designated as amorphousesomeprazole hydrate, is characterized by having broad X-ray diffractionspectrum as shown in FIG. 1.

According to one aspect of the present invention, a process is providedfor the preparation of amorphous esomeprazole hydrate, which comprises:

-   a) providing a solution of esomeprazole in the mixture of water and    a solvent or a mixture of solvents selected from tetrahydrofuran,    acetonitrile, 1,4-dioxane and dimethyl formamide; and-   b) precipitating amorphous esomeprazole hydrate from the solution.

The solution of esomeprazole may be prepared by dissolving esomeprazolein a mixture of water and the solvent or by dissolving esomeprazole inthe solvent and then adding water to the solution.

The solution of esomeprazole may also be prepared by adding an acid to asalt of esomeprazole in the presence of water and the solvent to obtaina solution of esomeprazole.

During precipitation the ratio of water to the solvent is maintained at0.5:1 to 4:1 by volume, preferably at 1:1 to 3:1 by volume and morepreferably at 1.5:1 to 2.5:1 by volume.

The precipitation of amorphous esomeprazole hydrate may be carried outby conventional methods such as cooling, seeding, partial removal ofsolvent, addition of extra quantity of water or a combination thereof.

The precipitated amorphous esomeprazole hydrate may be collected byfiltration or centrifugation and then dried.

The drying may preferably carried out at about 20-35° C. in rotovapour.

The amorphous esomeprazole hydrate is novel and forms part of theinvention. Amorphous esomeprazole hydrate may be used in pharmaceuticalpreparations.

Amorphous esomeprazole hydrate is useful intermediate for preparingamorphous or crystalline anhydrous esomeprazole.

Amorphous esomeprazole hydrate may, for example, be converted toamorphous esomeprazole by slurring with an insoluble solvent.

Esomeprazole hydrate may also be useful intermediate for preparation ofknown pharmaceutically acceptable salts by conventional means.

The above process may be used to purify crude esomeprazole or a crudeesomeprazole salt by providing a solution of crude esomeprazole andprecipitating pure esomeprazole hydrate as described above. The pureamorphous esomeprazole hydrate obtained is optionally converted toanhydrous esomeprazole by a method such as slurrying in an organicsolvent and filtering to obtain anhydrous esomeprazole.

Crude esomeprazole refers to esomeprazole for which further treatment isrequired to get esomeprazole of desired purity (pure esomeprazole).

According to another aspect of the present invention there is provided apharmaceutical composition comprising amorphous esomeprazole hydrate anda pharmaceutically acceptable carrier. Preferable pharmaceuticalcomposition is a solid oral dosage form.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an X-ray powder diffraction pattern of amorphous esomeprazolehydrate.

X-Ray powder diffraction spectrum was measured on a Bruker axs D8advance x-ray powder diffractometer having a Copper-Kα radiation.Approximately 1 gm of sample was gently flattened on a sample holder andscanned from 2 to 50 degrees two-theta, at 0.03 degrees two-theta perstep and a step time of 0.5 seconds. The sample was simply placed on thesample holder. The sample was rotated at 30 rpm at a voltage 40 KV andcurrent 35 mA.

The following examples are given for the purpose of illustrating thepresent invention and should not be considered as limitations on thescope or spirit of the invention.

EXAMPLE 1

Tetrahydrofuran (250 ml) and water (500 ml) are added to esomeprazolepotassium salt (50 gm) at 25-30° C., cooled to 20° C. and then the pH isadjusted to 7.5-8.0 with acetic acid. The reaction mass is cooled to 5°C., stirred for 2 to 3 hours at 0-5° C., filtered the mass, washed with50 ml of chilled mixture of water and tetrahydrofuran (2:1) and againwashed with water (100 ml). The wet cake is dried at 30-35° C. undervacuum to reach the moisture content to 25-30%. The solid is again driedin rotovapour at 25-30° C. under nitrogen atmosphere to give 26.3 gm ofamorphous esomeprazole hydrate (HPLC Purity: 99.92%, Moisture Content:4.0%).

EXAMPLE 2

Acetonitrile (250 ml) and water (700 ml) are added to esomeprazolepotassium salt (50 gm) at 25-30° C., cooled to 20° C. and then the pH isadjusted to 7.5-8.0 with acetic acid. The reaction mass is cooled to 5°C., stirred for 2 to 3 hours at 0-5° C., filtered the mass, washed with50 ml of chilled mixture of water and acetonitrile (3:1) and againwashed with water (100 ml). The wet cake is dried at 30-35° C. to reachthe moisture content to 30-35%. The solid is again dried in rotovapourat 25-30° C. under nitrogen atmosphere to give 26.1 gm of amorphousesomeprazole hydrate (HPLC Purity: 99.91%, Moisture Content: 4.1%).

1. A process for preparation of amorphous esomeprazole hydrate of whichcomprises: a) providing a solution of esomeprazole in the mixture ofwater; and a solvent or mixture of solvents selected fromtetrahydrofuran, acetonitrile, 1,4-dioxane and dimethylformamide; and b)precipitating amorphous esomeprazole hydrate from the solution.
 2. Theprocess as claimed in claim 1, wherein the ratio of water to the solventduring precipitation is maintained at 0.5:1 to 4:1 by volume.
 3. Theprocess as claimed in claim 2, wherein the ratio of water to the solventduring precipitation is maintained at 1:1 to 3:1 by volume.
 4. Theprocess as claimed in claim 3, wherein the ratio of water to the solventduring precipitation is maintained at 1.5:1 to 2.5:1 by volume.
 5. Theprocess as claimed in claim 1, wherein the precipitation of amorphousesomeprazole hydrate is carried out by cooling, seeding, partial removalof solvent, addition of extra quantity of water or a combinationthereof.
 6. The process as claimed in claim 5, further comprises theprecipitated amorphous esomeprazole hydrate is collected by filtrationor centrifugation and then dried.
 7. The process as claimed in claim 6,wherein the drying is carried out at about 20-35° C. in rotovapour.